1. Field of the Invention
The present invention relates to a process for clarifying algae-laden waste water stream to form a waste sludge and an effluent water stream having a lower amount of total suspended solids.
2. Description of the Prior Art
Algae-laden waste water streams are generally very expensive and difficult to clarity to low suspended solids levels. Normal sedimentation techniques (e.g., gravity-settling clarifiers) by themselves will not work with many algae species. The algae exhibits a specific gravity nearly equal to that of water and many species of algae live in the water in a highly dispersed manner. Besides these dispersed species not settling easily, they also may interfere with the settling of other solids that may be dispersed in water. In the past, it was found that if a coagulation aid was added to an untreated algae-laden waste water stream, coagulation would occur but settling would not rapidly follow.
Rather than directly trying to coagulate suspended solids in algae-laden waste water streams, persons skilled in the treatment of industrial waste water streams first attempted to control algal growth by adding copper sulfate or like chemicals to treatment ponds where algae was produced. See Kirk-Othmer, Encyclopedia of Chemical Technology, Second Ed., Vol. 22, pages 65-82 (1970). However, such chemical control methods have disadvantages. First, the use of chemicals like copper sulfate on a large scale can be expensive. Moreover, the addition of such chemicals to waste water streams introduces still other contaminants to such streams which may have to be removed later on.
Accordingly, there is a need in the art to improve conventional gravity-settling methods for clarifying algae-laden waste water streams without adding any further chemicals to these streams. The present invention is a solution to this need.